The invention relates generally to monitoring systems. More specifically, the invention relates to a system and method for computer-based, real-time monitoring and measuring of transient phenomena.
Transient phenomena pose a serious threat to systems that are exposed to such phenomena. Transients can occur at any time with varying amplitude, frequency, and duration. The energy of transient phenomena can couple into the electronic or mechanical components of these systems to cause temporary or permanent malfunction. Because of the potentially destructive nature of transients, therefore, industry has developed various transient-monitoring systems for detecting and measuring transients that occur near mission-critical systems.
A common source of one type of transient phenomena is lightning, which can threaten the successful operation of various mission-critical systems. For example, current procedures typically suspend launch operations of spacecraft in the event of nearby or direct lightning strikes until system level tests can be performed to ensure that the electromagnetic transients produced by the lightning have not damaged or disturbed the payload or launch vehicle systems. These retest operations are costly and often unnecessary. By placing electromagnetic sensors strategically near the payload and launch vehicles, an assessment of the potential damage caused by lightning-induced transients can be made from the transient information captured by these sensors. Other useful applications for transient monitoring include, for example, characterizing charging of spacecraft and monitoring transients on powerlines.
A purpose of a transient-monitoring system is to measure certain key parameters that are indicative of the potentially destructive nature of detected transients. These key parameters can include positive and negative peak amplitudes, duration of positive and negative transients, and the rate of rise of the positive and negative transients. Such parameters of transients have been empirically determined to correlate to problems experienced by electronic systems due to transients.
To characterize key parameters of transient phenomena, present transient monitoring systems often directly digitize the analog input obtained from the sensors. A microprocessor then quantifies the desired parameters from the digitized information. Such digitizers encounter problems, however, at high frequencies. To accurately capture transients at high frequencies, these digitizers need to sample the analog input at high sample rates, which require large amounts of computer memory to acquire the data samples. Consequently, memory capacity limits the duration for which the digitizer can collect data samples. Moreover, data sampling must be suspended to allow the processor to transfer the collected data representing the analog input out of the acquisition memory.
During this downtime, any analog input signals arriving at the digitizer are not sampled. In addition, this downtime can occur at inopportune moments. Any transient phenomena occurring during the downtime can go undetected and be lost. The high frequency transients associated with lightning, for example, can exacerbate the possibility of such an occurrence. The loss of such information may lead to an erroneous and potentially disastrous conclusion that the monitored system has not been exposed to harmful transients.
The invention features a computer-based transient pulse monitoring apparatus and method that are substantially free of the limitations of known digitizing systems. In one aspect, the invention includes a circuit board for use in a general-purpose computer system, including a processor, memory, and a digital signal bus for conveying digital signals. The circuit board is used for characterizing transient phenomena that occur at a monitored location. The circuit board comprises analog circuitry for receiving an analog input signal representing transient phenomena detected at the monitored location. The analog circuitry continuously measures a characteristic of the detected transient phenomena and produces an analog output signal representing the measured characteristic. The circuit board also includes a digital interface in communication with the analog circuitry and the digital signal bus. The digital interface converts the analog output signal into a digital signal representing the measured characteristic and transmits the digital signal onto the digital signal bus.
In one embodiment, the analog circuitry includes a peak detector for measuring a peak value of the characteristic attained by the analog input signal during a sampling interval. The peak detector comprises: (a) hold circuitry for holding the peak value; (b) input circuitry for providing a current value of the characteristic from the analog input signal; and (c) reset circuitry coupled to the hold circuitry and the input circuitry. The reset circuitry resets the peak value held by the hold circuitry to the current value at the start of a subsequent sampling interval. Consequently, resetting the sample-and-hold circuitry does not interfere with the continuous measurement of the transient characteristic.
In another aspect, the invention features a general-purpose computer system comprising memory, a motherboard having a digital signal bus, and a processor in communication with the memory and the digital signal bus. The computer system also includes a circuit board comprising analog circuitry for receiving an analog input signal representing transient phenomena detected at the monitored location. The analog circuitry continuously measures a characteristic of the detected transient phenomena and produces an analog output signal representing the measured characteristic. The circuit board also includes a digital interface in communication with the analog circuitry and the digital signal bus. The digital interface converts the analog output signal into a digital signal representing the measured characteristic and transmits the digital signal onto the digital signal bus.
In one embodiment, the computer system is connected to a network (e.g., the Internet). Other systems connected to this network can access information corresponding to the measured characteristic as the computer system produces and records the information.
In yet another aspect, the invention features a transient monitoring system that includes a transducer installed at a location exposed to transient phenomena. The transducer produces an analog input signal representing detected transient phenomena. The monitoring system also includes a sensor system coupled to the transducer. A general-purpose computer system of the sensor system includes a circuit board having analog circuitry for receiving the analog input signal representing transient phenomena detected by the transducer. The analog circuitry continuously measures a characteristic of the detected transient phenomena and produces an analog output signal representing the measured characteristic. The circuit board also includes a digital interface in communication with the analog circuitry and a digital signal bus of the computer system. The digital interface converts the analog output signal into a digital signal representing the measured characteristic and transmits the digital signal onto the digital signal bus.
In one embodiment, the computer system of the transient monitoring system is connected to a network over which other systems connected to the network can access information corresponding to the measured characteristic as the computer system produces and records the information.
In still yet another aspect, the invention features computer system connected to a client-server network. The computer system includes a transient monitor that produces data representing a characteristic of transient phenomena detected at a monitored location. A processor stores the produced data in a format that permits access to the data by other computer systems on the network.
In still another aspect, the invention features a method for monitoring transient phenomena. At a circuit board in a general-purpose computer system an analog input signal representing transient phenomena detected at a monitored location is received. A characteristic of the detected transient phenomena is continuously measured at the circuit board. On the circuit board, an analog output signal representing the measured characteristic is produced. The analog output signal representing the measured characteristic is converted on the circuit board into a digital signal representing the measured characteristic. The digital signal is transmitted onto a digital signal bus in the general-purpose computer system. The measured characteristic can be sampled at periodic intervals without interrupting the continuous measuring of the characteristic.
In one embodiment, a peak value of the characteristic attained by the analog input signal during a sampling interval is measured. A current value of the characteristic from the analog input signal is provided. The peak value is reset to the current value at the start of a subsequent sampling interval.